It is often necessary to protect sensitive component assemblies, such as circuit boards, from damage due to the environments in which they are being used. Since the electrical components that reside on the surface of these circuit boards are particularly sensitive, damage to these components can result from contamination and corrosion due to dirt, dust, moisture, mildew, or other penetrants such as diesel fuel, etc. coming into contact therewith. Also, physical damage to the electrical component may occur due to direct impact, vibrations, abrasion, handling, etc.
It is known to encapsulate electrical components. For instance, encapsulation to protectively surround a component has traditionally been achieved by encasing the component with a hard polymeric casing and thereafter using silicone, polyurethane, epoxy, or hot melt adhesive to encase the component within the hard casing. The polyurethane or epoxy encapsulating materials are typically injected into the casing at a low pressure to surround the electronics and then is cured in place to position the electronics within the casing.
A problem with known encapsulation methods includes the corrosion or degradation of the sensitive electrical components when moisture penetrates the encapsulant and contacts the components. Moreover, in applications when the component assembly is subject to vibration, the electrical components may debond from the encapsulant. This results in an entry being created for moisture or debris within the encapsulant.
Another problem with the traditionally manufactured assemblies includes providing a sealed, hard outer casing, which is often the most expensive constituent of the package. Further, the hard casing design is usually manufactured by first creating a series of molds that are significantly expensive and not subject to easy design modification. Also, during the assembly process there are multiple steps required to position and encapsulate the component to the casing at additional added expense.
One such example of a known component assembly is disclosed by U.S. Pat. No. 5,755,026. A plastic foam is formed to a desired shape to surround the components. Unfortunately, multiple steps are required to form such an enclosure and the foam filler does not offer enough protection from contamination or impact.
Another example of a component assembly is disclosed by U.S. Pat. No. 5,736,190 is more complex method of fighting moisture and debris, using a reaction of two oligomers to create a cured co-polymer layer around an electrical component. However, this patent is directed at being a moisture barrier and does not provide for any protection from physical damages or impacts that could occur to the component.
Another example of a component assembly is disclosed by U.S. Pat. No. 6,458,628 which discloses a semiconductor chip attachment with a dielectric layer. The dielectric layer is attached to the semiconductor with a thixotropic fluid that is cured to form an encapsulant. Unfortunately, there are multiple steps required to form the dielectric layer and subsequently attach it to the semiconductor chip.
Another known encapsulation assembly is disclosed by U.S. Pat. No. 6,439,698 which discloses a method for creating a dual function encapsulating material. The disclosed epoxy material has two cure mechanisms. After the material is applied to the electrical connections, a first cure is initiated by radiation to crosslink the epoxy materials and encapsulate the electrical connections. Then a second cure is performed with heat to adhere the electrical connections to the body of a cartridge. However, the process by which the materials are joined tends to be time consuming resulting in a multiple step process which is expensive to implement.